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Week 12/ Unit 12: Chapter 17

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Department
Physics
Course
PHYS 1600
Professor
Mike Massa
Semester
Fall

Description
Week 12 Summary Chapter 17 Quasars and Other Active Galaxies Quasars Quasars emit more energy each second than the sun does in 200 years and they continue to do so for millions of years Our knowledge of quasars began with amateur astronomer Grote Reber who built the first radio telescope in 1936 in his backyard Reber discovered Cygnus A a constellation hard to categorizeBecause Cyg A is one of the brightest radio sources in the sky its enormous distance intrigued astronomers although barely visible Cyg As radio waves can be picked up by amateur astronomers with backyard equipment which means its radio energy output must be colossal Cyg A shins with a radio luminosity 10 7 times as bright as the radio emission from an entire ordinary galaxy such as Andromeda Because of their starlike appearances and strong radio emissions 3C 48 and 3C 273 were dubbed quasistellar radio sources a term soon shortened to quasars Related objects called quasistellar objects QSOs also look like stars but have strong energy outputs in all different parts of the electromagnetic spectrum with most being strongest in the infrared More than 200000 quasars and QSOs have been discovered All quasars have redshifts of at least 006 or 6 of the speed of light Plotting their distances astronomers found that quasars began forming early in the life of the universe their numbers peaking about 2 billions years after it come into existence and their numbers dropping to nearly zero about 7 billion years ago A typical large galaxy like our own Milky Way contains hundreds of billions of stars and shines with the luminosity
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